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<article class="note remark-like"><h3 class="heading">
<span class="type">Note</span><span class="space"> </span><span class="codenumber">1.1.1</span><span class="period">.</span>
</h3>Equations involving derivatives are called differential equations. If the derivatives are only ordinary such as <span class="process-math">\((\ref{eq1_1} a)\text{,}\)</span> then these equations are called ordinary differential equations (ODEs). If the equations involve partial derivatives such as  <span class="process-math">\((\ref{eq1_1} b)\text{,}\)</span> then they are called partial differential equations (PDEs).</article><span class="incontext"><a href="sec_1-intro.html#note-1" class="internal">in-context</a></span>
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